TopGear drives the Merc SLS AMG GT3

Why buy an AMG? Two main reasons, according to official research: for the performance and the noise. Watching an SLS GT3 hammering down Ascari's pit-lane straight, bellowing like a wounded buffalo, it's hard to think of a more explosive way of internally combusting a few litres of hi-octane unleaded. Performance and noise? These guys have got the template down, and never mind that they're going to be first to market with a near-silent pure-electric supercar when the electric drive SLS lands in less than six months.

They're also very astutely ‘building the brand'. Buy a new AMG Mercedes and your chassis number qualifies you to join what's called the AMG Private Lounge. After five years in the game there are now more than 20,000 members, which makes for a hell of a high-net worth data base and some dynamic forums. Take it a step further and splash out on a Private Lounge driver training day, and you might find yourself on the pit-wall at Ascari looking at a bellowing SLS GT3. A GT3 you're about to drive. So much for the cliché that Germans don't have a sense of humour.

Mind you, there are a few hoops to jump through first, not to mention a few cones that need to be slalomed. Day one breaks down the tricky and technical Ascari circuit - reckoned by some bloke called Fernando Alonso to be the toughest in the world, but what would he know? - into three chunks. Learning these chunks in, variously, an AMG CLS63, SLS and best of all the insanely good C63 Black Series beats my original driving instructor George's Datsun Sunny (Cuban heels with lifts, wispy ginger 'tache - George, not the Sunny).

Affable Berlin-born racer Roland Rehfeld leads my pack of seven cars, and offers an often wry, occasionally spiky running commentary as we stitch together the racing line around this 5.1km track like a bunch of student surgeons with sides of ham for hands and flippers on our feet. By the end of the day, though, I'm somehow lapping Ascari in the SLS about as fast as he is, squeezing all I can out of the car without triggering any tyre squeal, provoking the traction control or indeed driving into a tree (of which there are many at Ascari). The training really works.

Day two sees an auto-test that pits my team against a coned sub-section of track and the immovable enemy that is time itself. This is precision stuff, especially now that the heavens have opened, and it's quickly clear that power-sliding a C63 coupe round the course, while fun and impressive to watch, is also a drastically retarded way to go. A German gentleman in big glasses by the LED timing board is similarly unimpressed when I slither to a halt in the end box with a cone impaled neatly in the centre of the AMG's three-pointed star. This will never do. Two veterans of previous driver academy events, Dave and Scott, set blistering times, and Team Yellow will go on to win overall, mainly because we don't incur any penalties by knocking any cones over. Roland is pleased and a little stunned that we have actually learned something.

By the time former F1 driver and Le Mans star Karl Wendlinger is readying me for my stint in the SLS GT3 I'm both adrenalized and in need of a quick lie-down. Since debuting in 2010, the SLS GT3 has racked up 37 race victories, and despite its fantastically aggressive appearance - has anything got a bigger rear wing than this thing? - Wendlinger, Rehfeld and Mercedes DTM legend Bernd Scheidner all tell me that it's surprisingly friendly. This is good to hear, because it's now absolutely pouring. ‘The track has an amazing amount of grip, despite the conditions,' Schneider says, mustering all the reassurance he can though it must be said that motorsport probably remains a better career bet for him than, say, counselling. ‘I'm only a second or two slower than I would be on a full dry set-up.' He is also, however, a four-time DTM champion.

Thanks to the FIA's ‘balance of performance' equivalency rules, the SLS GT3 runs 552bhp, slightly less than the road car. But at 1350kg, it's also much lighter, and considerably trickier to get into. The seat is a huge, all-enveloping carbon item, but the instrument layout is easy to fathom, and overall it feels functional, purposeful and surprisingly comfortable (most racing cars tend to be like this, but you wouldn't get far in battle if they were the equivalent of a medieval Iron Maiden, would you?) ‘It was designed to be as easy as possible to drive,' Rehfeld confirms, ‘and everything is built around the driver.'

A firm prod of a surprisingly small and nipple-ish starter button wakes the beast. Even at idle it makes the most magnificent noise, a martial beat overlaid with a rather flatulent blare. Press the clutch, engage first with a hearty mechanical thump using the column-mounted paddle, and ease away on around 3000rpm. Wendlinger is up ahead in a regular SLS.

It is immediately overwhelmingly brilliant. We're on wets, and we will never go fast enough to generate decent heat in the rubber or brakes, and Wendlinger is keen to return to base without having to explain why his charge fell off the track, but even so the immediacy of the thing and the purity of its responses floods your system like a fast-working narcotic. There is grip to spare, even in these conditions, and it powers forward with relentless determination, shrieking and parping and gurgling.

Suddenly the thought of monstering one round the Nordschleife in the middle of the night doesn't seem quite so scary. Then again, civilisations have risen and fallen in the gap between where I begin to brake and where I actually should be starting to brake. Having raced a bit, this confirms my theory that the world's best drivers aren't necessarily measured by how fast they can go, it's how good they are at slowing down that really counts.

After three short laps, it's all over. I feel like crying. The narcotic has me hooked, which is what always happens when I find myself in a decent racing car. ‘You have the best job in the world,' I say to Wendlinger, a seasoned SLS GT3 campaigner and pro endurance racer. ‘It is possible, yes,' he replies with a hint of a smile.